BURLINGTON - Health and public safety officials are warning heroin users that product sold as heroin and packaged in the same manner as heroin may instead contain pure fentanyl or fentanyl-laced heroin.

The Vermont Department of Health reported Thursady afternoon it has just confirmed the cause of three deaths in Addison County in January to be overdoses from pure fentanyl. Fentanyl is an opioid drug that is up to 50 times more powerful than heroin, and much deadlier.

"Heroin users may not know they are shooting up fentanyl, or they may not know just how deadly it is," said Health Commissioner Dr. Harry Chen. "Even a very small amount of pure fentanyl, just a few grains, can stop your breathing and kill."

Fentanyl generally is used intravenously in hospitals to treat pain.

Police said this week they are trying to develop information about the packaging source and distribution of the drug.